Saponins are considered as a diverse group of natural active compounds, which are widely found in crops. Mevalonate pathway (MVA) is regarded as the main pathway for synthesis of saponins in crops. This study aims to compare transcriptome of the leaf with tuber of crop including tubers and roots. First, more than 166 million reads were generated. The existence of 36,678 unigenes in the two samples out of 48,936 assembled ones showed a significant difference in expression. Finally, 310 and 290 highly up-regulated genes in leaf and tuber were selected for the next analysis. In addition, the expression profiles of 13 key genes in the MVA pathway were compared in RNA sequencing and reverse transcription-quantitative polymerase chain reaction analysis. The results indicated that cyclamen tuber has a higher level of expression of MVA pathway genes. The topological analysis for gene co-expression network involved in triterpenoid synthesis represented that the genes at the beginning of such pathway play a critical role so that the reduction of their expression challenges triterpenoid synthesis severely. The tuber of the cyclamen appears to be the major site of triterpene synthesis, and transfer of excess Isopentenyl pyrophosphate (IPP) from tuber to leaf activates downstream genes in leaf of crop.

皂苷被认为是一组广泛存在于农作物中的天然活性化合物。甲羟戊酸途径（MVA）被认为是作物中合成皂苷的主要途径。本研究旨在比较叶子与作物块茎（包括块茎和根）的转录组。首先，生成了超过 1.66 亿次读取。在 48,936 个组装的 Unigene 中，两个样本中存在 36,678 个 Unigene，表现出显着的表达差异。最后，选择了叶片和块茎中310个和290个高度上调的基因用于下一步分析。此外，通过RNA测序和逆转录定量聚合酶链反应分析比较了MVA途径中13个关键基因的表达谱。结果表明仙客来块茎中MVA途径基因的表达水平较高。对三萜类化合物合成涉及的基因共表达网络的拓扑分析表明，位于该途径起点的基因发挥着关键作用，其表达量的减少对三萜类化合物的合成提出了严峻的挑战。仙客来的块茎似乎是三萜合成的主要场所，过量的异戊烯焦磷酸（IPP）从块茎转移到叶子会激活作物叶子中的下游基因。